Take Two Opposing Corners and Tie Two Knots at the Center.
Slide the Remaining Corners Beneath the Knots, and Pull Each Corner Out From the Other Side.
Gather the Ears of the First Knots Into a Spherical Shape, Then Take One of the Unused Corners to Cover the Sphere. Tuck the End Beneath the Knots, Then Shape the Remaining Corner Into a Calla Lily.